Lens blocking device



July 22, T95? J. F. MGCARTHY ET AL 2,603,922

LENS BLocKm/G DEVICE F'iled Nov. 19, 1949 ,7 l INVEN-roRs ATTORNEY generally fr. rectangular in 1 shape.

Patented July 22, 1952 UNITED IAT-.Es PATENT fofFfFfIc-E .tionoiiNew York :'6 Gleim 1 :'.Thisjnventon:relateste lensibloekirlg .devices andzhas Particular referencefto'improvedfmeans foruhloekingfophthalmicllenses.

In 'the conventionalmanufacture of..ophthal mic lenses, azlensrblank ofzmoldedglass,is-ground andipolished'on zeach :.of; itsi two .sidesto carefully controlled curved surfaces#the; shapes andspatial :relation :of the two f curvedfsurfaces' :resultingin thenptical refraction desired. .Inthe various ..1gr'rndingi-and -polishingoperat9ns ato f-Which the.v blank; is subjected... iti is customary :to fsecure the-rblank'-vby: means of an'gadhesive,.rsuohrns; .m01- tenptcnf-to; a' lenszblock swhehf-ser'ves ars-.afhandle ;.or, couplingrmeans :byzwhich rthe .blank inlay be held and-controlled .This-operation islcalled @blocking-P 'Lens'fblocks `usually ;eonsiSt of ,a head, lhailingdarn-outer surfacesubstantially:conforming @to the :surface of the i blank :opposite tto, that.:on vwhich: it is :desired toc-werkend farsharjrk, AThe .--block :is fixed in :positionni-n the surfacing'maehlne .by means of :the shank, :rse -fthat 'the :blocked lens blank fbearsa .predetermined .relation to :the rest of :the machine.

The .areal iproblem :in blocking arises .fin connectionrwith asemi-'flnished lens, which is `a lens blank: onesurface oflwhich has: alreadybeen ground :and polished. vThe semi-'finished -lens mustfbe rvaflixed f to the lens' block .with` its Ifinished surface against the head lx1-1a;` known relatlonvto the block, in -orderfthatf the unfinished kouterlsur.- face of .the -blank may' be:so Viirlished -asfto bear the 'desired relation to-the frstf i'ln'ishedssurfaoe.

character is disclosed -in 'Lockhart Patent z,29o;56f's,l issued July 21, -=1942.V :The "blocking operation'propenollows Ithe above-describedimarking :ofv the semi-@finished lens. j Variouslingenious 'and complicated blockf ingdeviceszareknown, in which: theblank isfheld bglpping .means which permitthe operator to adjust 'the Vblank kmanually until the inkY marks ane Avisually Yaligned rwith indicia on the blocking device. :The blocking 'deviceis alsoprovded with means- "for holdingr la 'lens'-block Vin known relation-"to these imminenti (withmeansgfor swingnemesis@ @geen pen-.eri wenn@ ingtheggripped .lens blank to theheld blocker vice .versa After .the lens .blank .has ...been ually aligned, ther operator. coats .the block with molten pitch, and then manipulatesthe.. swing.. ing means `.to bring the blank, and.the.block.to gather... These ymaybe.called transfer-.type blockf.- ingldevies, and, although theyeareiwidelynsed, they are: subeot .110 en number .of disadvantages. ,The blocking device of rthe present..i1'nenfi ;}n isl simple, eompach inexpensive and leaSy m11 erate. By the use of indicia onitheheadinfethe lens `block and ,transparent ."pitch. all: ftnanser mechanism .is seliminated,- and the .visual .aligning vis, done .directly im tlille block itself, Means are provided 4for excludinstheeptchr fromcentain areas of the lens blank. order to .maintain e naar...areas.for use fas Ycal.iper-ing meinte. and .f1-Q1- otherfpurposeslto.beidescribed .Itis a .principal object. of this inventionto1 Pro. vide aLblocking. dev-ice. of-simpleoonstruetionthat mayreadily befkept y free of. undesirablepchgtaef.- cumulations. Y Other objects and advantages of invengtion .will-.be apparentgfromfthefollowing description,. taken imconnecticn withtheaecornpanying drawings; nwhich: l

l'f'lne` Lis. .a front elevation., of. a blocking-Jde.- vice according ,to .this invention, havinginserted therein a lens ...blockcarryng :a A.block dlens blank.:

Figure aplan fvlewf .ih eblooking.'

alone;

`liti-sure. sisY a.-tnmsverse@sectlonofv device. with. a. .lens lulockslrov'v.1.1.-lelenife.Y de ice Figuren. ,l Y. v.Referring more ;pantieularly-ito the` dnawings;

the.blockingldevicefogblockngqnead t0 omprlses .Alle

a .body portlonerlbase I.- l

portionforstopfplateHolen ur-11..: iecting. vieldillely-1n.ounted`n fingers :e The-besef fmeyeontenen'lyfbefvnth shane-.lle

maratea,andaehouowedfeutrentner@ option, r

Darts wbedescribedleter- The ton-plate. temen be retainedin position` on the` base l. I yni'any'll." venient mannersuchas byboltJA.

.The ,pins I3 are rmOllIlted `rfor vertical movement with respect tothe ,top plate'. L2y .and bas/e Il. and .are equally .spaced .fr .om..ean other. andiaboutithe. central vertical.axisgoflbf' H "The upperiends vof the pins I3 areprefer'aglglvjY scribed-hereinafter,

3. square as shown, to prevent rotation of the pins, and have their extremities chamfered vto form sharp, straight line edges i5. The square ends of the pins I3 fit snugly for smooth sliding movement in correspondingly shaped holes in the top plate I2,, The lcwer ends orstems le of pins I3 may bejcylindrical asv shown, and are slidably mountedy in holes I'I in the base Il. A compression spring I8 is coiled about each of the stemsV I6, and serves to yieldingly maintain the pin I3 in its extreme upward position shown in'Figure 3. To limit the upward movement ofthe pins I3, a

. seldom have pitch spilled Von it and the. presence of pitch adhering to the base l i would not intert fere with Athe proper operation of the blocking device, as it would on the top plate I2 and the pins I3.

A type of lens block especially suitable for use with the blocking head H3, is shown in detail in stop washer I9 is mounted'on each pin abutting against the shoulder formed between its square" upper end and its cylindrical lower end, andy is retained in that abutting position b y a Ysnap washer 20 tting in a groove 2| on the'ste'm I6 in conventional manner.

The top plate I2 is provided with a transverse IvAccording to thisinvention, the top' platefIvZ andV the pins. I3 aremade of cil-impregnated,

porousmeht'al such as 'that soldlnunder the' trade}- markjOilitcPf V'Such porous metal parts are made k, as will be de- Figures 3, e and 5. The lens block 2li of these gures comprises ahead 22 and a shank 25. As

Will be understood by those skilled in the art, the upper lsurface 26 ofthe head 2li is shaped to conform to the surface or" a particular semiiinished VlensY blank, a variety of lens blocks being employed to take care Vof diierent kinds of lens blanks. Sincethe conventional seminished ophthalmic lens blank is 50 mm. in diameter, the head 2t may convenientlybe made of trisdiameter,` although,A obviously, it may be of any desired size. The'shank 25 is generally rectangular in shape, and is of such Widthas to fit easilybut snugly in the Vslot v22 of the blocking head lil, 'so-that thelens block 23 may beplaced in the blocking/head I0 in .only .one of portions. y Second, thepowdered metal compound f is-compressed to the desired shape and size inY a briquetting die. Third,V a sintering heat treatment transforms the fragile briquet into. strong, .porous metal. Fourth, lthe part is sized .by press-Y inertemissed dimensions'in @sizing da Fifth,

the porous metal part vis 'imr'gregnated4 withnongumming lubricating oil by immersion in ,aj bath vof oil-Atheporous metal absorbing the oil by capillaryactionfjust asralspongeabsorbs water. Y

We have found that molten pitch such as is Vused inblockingophthalmic lenses, willl not adhere, upon cooling, to parts made from oil-impregnated, porous metal of the -,character just described. Accordingly; bymaking lthe parts ofour blocking device that are exposed to contact with. molten pitch lof this porous VmetalQour "blocking device may easily be kept cleanjand clogging of the freeoating pins I3 is prevented. Any Ymolten pitch that may accidentally come in vcontract with the tpfplate I2 and pins AI3 may be removedwith-V out dilculty, the oil present in the metal preventingl adherence `of thepitclrtofthe metalpart.

Contactwith molten' pitchtends to remove the Oil frornthe `metal parts, and it istherefore necesi' sary; from time totime, to replace the oil;V This may readily be done by cleaning Lthe parts,.apply-y ingrtothe'm apliberal coating of a suitable nongumiriing lubricating` oil, such as' SAE 20 motor oil; and allowing this coating to remain on overnight. After continued use, such overnight soaking with oil may not suiice to replace the lost oil. in which case the top plate l2 and the pins I3 may be completely recharged with oil by dis-assembling the device and soaking the top plate and hour;

The'lens block 23 is provided-'with three hard. ened steel inserts 21 having .g conical recesses therein and pressed intoV shank 25. "Foev inserts 2l' facilitate the use of the block 23 in'connection vwith oscillating grinding. or. polishingfmachines-such as described in United States Patents As thus 'far`,describedztheflens block :23j is conventionalv exceptV for its rather large; diameter.' 'In'addition, theflens block 23 .is provided with milled cross-lines `zii and 22, interseating at right. anglesv at `the central vertical `axis ofthelensblock 23, and with four sub- YstantiallyY rectangular recesses 353 at its :periphery-which are aligned with the cross lines and are adapted to receivethe pins I3 :of the blockinghead I0'. The cross line 28is disposed vertically above the longitudinal axis ofi thershank 25, andV is. preferably made vlonger thanjthe cross line 29't'o'visually indicateA the 'location of .the shank to an operator lookingdown on' the top of the'lens'block 23, thus facilitatingl the insertion of the lens block in the blocking head IS.

In'using the Vblocking head mythe operator is provided withLa semi-nished lens blank such 'as the lens blank SI shown in Figure '1, suitably marked as above described, and a matching lens block 23. These are first warmed on hot plates toappropriate temperatures in the customary 'mannen -The operator then picks up'the lens head quantityhof molten transparent pitch onl theupblock 23, holds it so thatitsline 28 is .in alignwith the, slot 22 as above Vdescribed to center theilens block- 23v with respectpto the blocking I 6. 'Ihe operator thenV rpours ar small per surface 26 of thelens block, the operator readily becoming sufliciently skilled to `employ a'quantity of the molten pitch which is` just` sufficientto substantially coverthe lens block when thalens .is pressed downfon the molten pitch. Thepperator then picks up the marked lens blank 3|, and holds it .over the, lens block. -By looking directly downv on the assembly, the operator may readily visually align the ink marks on the blank 3I with'the Vcross lines 28 and 29 fiaeosgeez 5 f 'cIi"flI-lie.blcck. ALWluznth'eecper:iterobservesfthat fthe-'Center Vdet offf'theslens blank'iis'iali'gnedwwith fthe intersection lofi the.' cross vlines28iand::2d-'clarin -the lens-blankeaxis' is aligned-with ithetcrossili'ne Semi-lie presses'rithe lens' "blank L23 IlA dowx'nlomfme Imolten;pitcm, and, holdsf-thelens blankiin...tliat position ;;:unti1..;-the pitch, coolssandfharrlensifzto "fo'rma bond :between :the l lens i. blank :andctl'ile -b`lo'c`k,;asl indicated atlf32-Sinigure'l. The

iblockedL-lens and. lenslbliockv mayv then :be :re-

rmoved :from4 *the i' blocking fhead m for ifm-.ther operations in the appropriate surfacingmachine. 1; :When the operator-gently `pir-:sseszthe lens fblankil down'. on :the rlensablcck .fas iabove described; :thea-sharpvupper edges I .5210i '.-theipins iI-'engageithie f under :surfaces fof a the fslensfrblank .lbeior-eithetfblank ,f contacts :the amolten'spitch, and -the eo'ntinuejd downwardnum-:mentA ioffthe'lens blank as the blank is firmly seated'onrthezblock, carries :thefyieldingminsIS down with it. The sharpI-edges d .thus lcontinuously engage the under surface of. the lens blank during the blocking operation, and-'preventy the pitch from .flowing on to the --areas ofthe-lensblank .under surface lthat are coextensive -.with .the 'recess 30. The 4incite-n.pitch onthesurface 26 ows around -the pins I'3 to the edge of'theblock head 24, and. if too much pitchis. used, the excess may 'dropfonto fthe-.top..plate .l 211211; :has beenifound .that `pins lprovidedwithstraight line, sharp upfper. edges 11.5.. as. illustrated i inFigfure .3, iivilll''successful'ly;exelude pitch from areas abovelfd'escribecl .when vnsedwith flenssiblanks the Vlinder surfaces of which vary from plano to plus or minus 16. diopters. This is sufficient to accommodate the blanks normally found in practice. For extreme sizes of lens blanks, the upper edges I5 of pins I3 could of course be shaped to correspond to the blanks.

It has been found that Very little pitch adheres to the top plate l2 and pins I3 when they are made of oil-impregnated, porous metal.

isitothave fprisx, `fthe.'fp-rismifmay :be intnoduced by suitable adjustment of the suniiaciiig'machine whichitheblockedlensblank e'mounted With' omelftylpcs of isurfacimachines, r'heJI/evier, it' l.isi neces'sary-tcy 'introduce the desired amount-erhmmm mccnnectioniwith' tnebiocking operation. Tliiszm-aylbeaccomplished by "using curi blockingliheadtogether A with :afftransfe-r ty-pe f0f2lbloekling devic'el'su'ch aiscal-bove-iclescrbed.v

The pi-tchefree ar-eas." on he under surface 'of the lens'blank 3 If are useful =asfcaliperingf poi-nts 'tddetermine lens thickness during processingof the *blocked lens 1 i-n L1'surfacing machines. Edge calipering l-is` generally preferred, but Avcertain types of surfacing machines are so designed-faste re- *fqu'i-re; calipering atthe center` of f the lens :blank through la centrali @hole provided inthelensl block. 011-17bleek-ing 'head mair `readily zbe adapted 'for :user central, v VVAfuric'tioning'similarly to theiingers fI3; to keep ace'ritr'alpot o the'under-surface of Vthe-'lens `1blankf=1fre`effrompitch. l tch-free" `.rea produced-bythej-pins lf3 "lcc'atdas tepermit the-fuse offthe'blocked -chuek's off-thetype liavingfour'regis- :t ringffpinslocatedj 'at opposite ends* of lcrossed What little pitch does adhere to these parts may be easily and completely broken away by the operators ngers as soon as the blocked lens and lens block have been removed from the blocking head I0. All surfaces that may come into contact With the lens block 23 and the lens blank 3I may therefore easily be maintained free from minute spots of pitch which would, if present, interfere with the accuracy of the blocking head IU.

Although the above-described lens block 23 is the preferred form for use with our blocking head, it Will be apparent that other forms may successfully be used. Shank 25 may be formed in any desired irregular shape so long as the slot 22 is shaped to conform with it. Although desirable, the recesses 30 are not essential, and, in lieu thereof, the lens block may have a circular periphery such as to t Within the pins I3, as indicated by the broken line 33 in Figures A4 and 5.

diameters offithechuck: i l The registeringpinsof 'suchL chucks requireftheunder surface of the blank at the four points ati/Which vthey engage, 'tdfbeffree `from:pitch'vand other accumulations,l in forder vtcffmaintain vaccuracy of 'registration l"of the'bl'o'cked lens :inthey chuck. y-Ourblockinghead is therefore especially useful for blocking lenses f to be mounted in such chucks.

preferred form, it is to be understood that the L invention is notlimited thereto but may com" prehend other arrangements of v parts, details and features Without departing from the spirit of the invention. We desire to be limited, therefore,

only by the scope of the appended claims.

We claim:

1. A device for centering and axially aligning 'n a lens blank on a lens block supported in the device While securing the blank to the block with molten adhesive deposited on the lens block, comprising a block-receiving portion, and means associated with said block-receiving portion for centering the block With respect to the device, said portion and said means being made of sintered porous metal and being impregnated with oil so as to be easily cleaned of Said adhesive.

2. A device for centering and axially aligning av lens blank on a lens block while securing the blank to the block with molten adhesive deposited on the lens block, comprising a block-receiving portion and a finger-like member slidably and resiliently mounted therein vand adapted to project past the lens block to yieldingly contact and mask from said adhesive a portion of the under surface of the lens blank to be secured to the block, said block-receiving portion and member being made of sintered porous metal and being impregnated `with 'oil` selvas; to l'be easily 1 cleaned Y of said'adhesive. Y 1;. M I

3. A. device VAforl centering -andzaxially .aligningaliens blank';on Ya lens blockwhile securing the blank to the-.block with molten adhesive deposited on thegf lens `block, f comprising a block-receiving portion andlnger-likevmembers slidably and impregnated `with oilso` as to be easily cleaned ofv said adhesive. A. p i, f ,4.1. In alens blocking device, a supporting base having anVA upper'k portion adapted to receive a 'slidably andresiliently mounted in and projecting -above said base and adapted to 'extend beyondthe lens block and within the margin of said fingers yieldingly contatthe vunder surface ,of a lensV blankrcentered on the block and serve to mask portions ofv such vunder surface from the .adhesive used to secure theflens blank to the lens block, a. plurality of nger-lke members a lens blankA centered above the block, wherebyV block, and saidblock-receiving portion and mem- Y bers being made of sintered porous VmetalVV and cleaned of said adhesive.

' 5. In a lens blocking device. a supportingfbase having an v'upper portion recessedrto receive lthe shank of a lens block, a plurality of finger-like being impregnated with oil so as to be easily l :members slidably:mountedY in said baseyspring means for normally projecting the finger-like Y f ,members vabove said: base, `said members 'being yso located. as to engagethe periphery of a lens block in'sertediin thev 'device togcenter -the block with `respect to the device, and said members beingof such'length as to extend beyond the thus-centered lens block and yieldingly contact the underfsurface ofa lens blank centered on the block to mask portions of such unders'urface from the adhesive used to secure the lens blank totheblock. Y 6. A lens blockingY device as claimed in'claim 5 in which said upper portion of the supporting base and said finger-like members are madefof sintered porous 'metal and are'impregnated'with oil, whereby any of said adhesive contacting said upper portionand members may be-readilyremoved therefrom. Y,

- l JAMES F. MCCARTHY HENRY T. FLUCK.

v,rnsr'feimsNons errno 1 The following referencesa'reV of record in the file of Vthis p'atent: Y vI nvrrrn .STATES PA'IENTS Number 1, Name Date Y Re. 18,569 McCabe Aug. 16, 1932 1,284,283 Flad Nov. 12, 1918 1,556,658 Williams Oct. 13, 1925 1,642,347 Williams e v Sept.v 13, 192'? Fritzsche Mar. 22, 1949 

